There are many types of evaporation devices for volatile substances, generally air-fresheners and/or insecticides, which utilise a wick, a spray, a permeable membrane, gel or impregnated paper as the medium for the evaporation of said substance.
These appliances need means which allow their activation by the user, and in some applications means for the automatic activation or deactivation, for which reason they employ light sensors to select different uses of the device during the day and at night, or to activate the evaporator for example when the user is present.
In certain applications like for example for the diffusion of a volatile substance inside a vehicle, the known sensor-equipped devices do not offer satisfactory benefits, since they do not only detect the presence of movement or luminous conditions inside the vehicle, but are also sensitive to movements or light conditions outside the vehicle, for example a person passing on foot near the vehicle.
Thus the known devices with automatic operation are not appropriate for their use in a vehicle in that the mere proximity of a person to the vehicle can initiate the evaporation of the substance, producing an unnecessary waste thereof and an unpleasant aromatic saturation inside the vehicle.